A study on the recovery of Tobago's coral reefs following the 2010 mass bleaching event.
TL;DR: The juvenile distribution and the response of individual species to the bleaching event support the notion that Caribbean reefs are becoming dominated by weedy non-framework building taxa which are more resilient to disturbances.
About: This article is published in Marine Pollution Bulletin.The article was published on 2016-03-15 and is currently open access. It has received 17 citations till now. The article focuses on the topics: Resilience of coral reefs & Environmental issues with coral reefs.
Summary (1 min read)
Jump to: [2.2.4 Statistical analysis ] – [2.3.1 Juvenile density and composition ] and [3.4 Discussion ]
2.2.4 Statistical analysis
- All juvenile and sediment data were tested for normality using the Shapiro-‐Wilk test and homogeneity of variance using graphical methods.
- Sedimentation rate data were found to be normally distributed, although juvenile data did not follow a normal destruction.
2.3.1 Juvenile density and composition
- Broadcasting juvenile taxa represented the minority (27.1 %) such as Siderastrea, Diploria, Montastrea and Colpophyllia.
- The small-‐sized brooding Scolymia spp., had moderate abundances of juveniles, mainly at Culloden sites.
3.4 Discussion
- Many species experienced a decline in colony abundance; percent cover and mean colony size by 2011, symptomatic of corals having suffered complete mortality and/or partial mortality.
- This study indicates that across Tobago’s different reef sites, the bleaching disturbance can lead to a dominance of smaller size coral colonies, which could negatively affect the reproductive output.
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TL;DR: How coral communities have changed in the northern sector of the Mexican Caribbean between 1985 and 2016 is evaluated, and the implications for the maintenance of physical reef functions in the back- and fore-reef zones are evaluated.
Abstract: Functional integrity on coral reefs is strongly dependent upon coral cover and coral carbonate production rate being sufficient to maintain three-dimensional reef structures. Increasing environmental and anthropogenic pressures in recent decades have reduced the cover of key reef-building species, producing a shift towards the relative dominance of more stress-tolerant taxa and leading to a reduction in the physical functional integrity. Understanding how changes in coral community composition influence the potential of reefs to maintain their physical reef functioning is a priority for their conservation and management. Here, we evaluate how coral communities have changed in the northern sector of the Mexican Caribbean between 1985 and 2016, and the implications for the maintenance of physical reef functions in the back- and fore-reef zones. We used the cover of coral species to explore changes in four morpho-functional groups, coral community composition, coral community calcification, the reef functional index and the reef carbonate budget. Over a period of 31 years, ecological homogenization occurred between the two reef zones mostly due to a reduction in the cover of framework-building branching (Acropora spp.) and foliose-digitiform (Porites porites and Agaricia tenuifolia) coral species in the back-reef, and a relative increase in non-framework species in the fore-reef (Agaricia agaricites and Porites astreoides). This resulted in a significant decrease in the physical functionality of the back-reef zone. At present, both reef zones have negative carbonate budgets, and thus limited capacity to sustain reef accretion, compromising the existing reef structure and its future capacity to provide habitat and environmental services.
40 citations
TL;DR: Investigating coral community composition across three different temperature and productivity regimes along a nearshore-offshore gradient on lagoonal reefs of the Belize Mesoamerican Barrier Reef System suggests that corals utilizing these two life history strategies may be better suited to cope with warmer oceans and thus may warrant protective status under climate change.
Abstract: Coral reefs are increasingly threatened by global and local anthropogenic stressors such as rising seawater temperature, nutrient enrichment, sedimentation, and overfishing. Although many studies have investigated the impacts of local and global stressors on coral reefs, we still do not fully understand how these stressors influence coral community structure, particularly across environmental gradients on a reef system. Here, we investigate coral community composition across three different temperature and productivity regimes along a nearshore-offshore gradient on lagoonal reefs of the Belize Mesoamerican Barrier Reef System (MBRS). A novel metric was developed using ultra-high-resolution satellite-derived estimates of sea surface temperatures (SST) to classify reefs as exposed to low (lowTP), moderate (modTP), or high (highTP) temperature parameters over 10 years (2003 to 2012). Coral species richness, abundance, diversity, density, and percent cover were lower at highTP sites relative to lowTP and modTP sites, but these coral community traits did not differ significantly between lowTP and modTP sites. Analysis of coral life history strategies revealed that highTP sites were dominated by hardy stress-tolerant and fast-growing weedy coral species, while lowTP and modTP sites consisted of competitive, generalist, weedy, and stress-tolerant coral species. Satellite-derived estimates of Chlorophyll-a (chl-a) were obtained for 13-years (2003–2015) as a proxy for primary production. Chl-a concentrations were highest at highTP sites, medial at modTP sites, and lowest at lowTP sites. Notably, thermal parameters correlated better with coral community traits between site types than productivity, suggesting that temperature (specifically number of days above the thermal bleaching threshold) played a greater role in defining coral community structure than productivity on the MBRS. Dominance of weedy and stress-tolerant genera at highTP sites suggests that corals utilizing these two life history strategies may be better suited to cope with warmer oceans and thus may warrant protective status under climate change.
26 citations
Cites background from "A study on the recovery of Tobago's..."
...in the Caribbean [25] and continued decline is expected as temperature stress increases [6, 26, 27], leading to a decline in reef complexity [28] Temperature Regimes Impact Coral Assemblages of Lagoonal Reefs...
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...A shift from dominance of competitive and generalist species to weedy and stress tolerant species occurred on Okinawan reefs following the 1998 El Niño bleaching event [29, 30] and an overall decline in coral cover and abundance currently occurring in the Caribbean has been coupled with an increase in abundance of weedy species [27, 31]....
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TL;DR: The results reinforce the notion that corals are sensitive to anthropogenic changes and reveal the scarcity of information on coral responses to pollution, tourism, overfishing and acidification, particularly in mesophotic ecosystems and in ecoregions outside the Indo-Pacific and Caribbean.
23 citations
TL;DR: It is postulate that the decline in skeletal extension rates for nearshore corals is driven primarily by the combined effects of long-term ocean warming and increasing exposure to higher levels of land-based anthropogenic stressors, with acute thermally induced bleaching events playing a lesser role.
Abstract: Anthropogenic global change and local stressors are impacting coral growth and survival worldwide, altering the structure and function of coral reef ecosystems. Here, we show that skeletal extension rates of nearshore colonies of two abundant and widespread Caribbean corals (Siderastrea siderea, Pseudodiploria strigosa) declined across the Belize Mesoamerican Barrier Reef System (MBRS) over the past century, while offshore coral conspecifics exhibited relatively stable extension rates over the same temporal interval. This decline has caused nearshore coral extension rates to converge with those of their historically slower growing offshore coral counterparts. For both species, individual mass coral bleaching events were correlated with low rates of skeletal extension within specific reef environments, but no single bleaching event was correlated with low skeletal extension rates across all reef environments. We postulate that the decline in skeletal extension rates for nearshore corals is driven primarily by the combined effects of long-term ocean warming and increasing exposure to higher levels of land-based anthropogenic stressors, with acute thermally induced bleaching events playing a lesser role. If these declining trends in skeletal growth of nearshore S. siderea and P. strigosa continue into the future, the structure and function of these critical nearshore MBRS coral reef systems is likely to be severely impaired.
21 citations
TL;DR: This article examined differences in coral and algal community compositions and their response to human disturbance and past heat stress, by analyzing 25 sites along a gradient of human disturbance in Majuro and Arno Atolls of the Republic of the Marshall Islands.
11 citations
References
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TL;DR: The majority of recruits were non-massive scleractinian species that contribute relatively little to overall reef-building processes, a finding that is similar to previous studies.
Abstract: This study examines scleractinian zooxanthellate coral recruitment patterns in the Florida Keys to determine if differences in density or community composition exist between regions. From July to September 2002, nine patch reefs, three in each of the upper, middle and lower Keys, were surveyed for coral recruits (colonies <5 cm in diameter) using randomly placed quadrats and transects. Coral recruits were enumerated, measured, and identified to genus. Fourteen genera of corals were observed across all sites and ranged from five to 13 per site. Densities ranged from 6.29 ± 1.92 (mean ± SE) to 39.08 ± 4.53 recruits m-2, and there were significant site and regional differences in recruit densities. The density of recruits in the upper Keys was significantly lower than in the middle and lower Keys. In addition, the upper Keys were less diverse and had a different recruit size-frequency distribution. The majority of recruits were non-massive scleractinian species that contribute relatively little to overall reef-building processes, a finding that is similar to previous studies. Fewer recruits of massive species were found in the upper Keys compared to the middle and lower Keys. The recruitment patterns of the reefs in the upper Keys could potentially hinder their ability to recover from stress and disturbances.
34 citations
"A study on the recovery of Tobago's..." refers background in this paper
...A low juvenile population dominated by brooding taxa with weedy life history strategies is common across Caribbean reefs (Miller et al., 2000; Moulding, 2005; Irizarry-soto and Weil, 2009; Manfrino et al., 2013)....
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TL;DR: The results indicate that when the confounding effects of colony density and size were removed, selective corallivory existed only for the less dominant Porites porites, suggesting the projected success of P. porites on Caribbean reefs through high reproductive output, resistance to disease and rapid growth rates may be attenuated through selective corAllivory by parrotfish.
Abstract: The past few decades have seen an increase in the frequency and intensity of disturbance on coral reefs, resulting in shifts in size and composition of coral populations. These changes have lead to a renewed focus on processes that influence demographic rates in corals, such as corallivory. While previous research indicates selective corallivory among coral taxa, the importance of coral size and the density of coral colonies in influencing corallivory are unknown. We surveyed the size, taxonomy and number of bites by parrotfish per colony of corals and the abundance of three main corallivorous parrotfish (Sparisoma viride, Sparisoma aurofrenatum, Scarus vetula) at multiple spatial scales (reefs within islands: 1–100 km, and between islands: >100 km) within the Bahamas Archipelago. We used a linear mixed model to determine the influence of coral taxa, colony size, colony density, and parrotfish abundance on the intensity of corallivory (bites per m2 of coral tissue). While the effect of colony density was significant in determining the intensity of corallivory, we found no significant influence of colony size or parrotfish abundance (density, biomass or community structure). Parrotfish bites were most frequently observed on the dominant species of reef building corals (Montastraea annularis, Montastraea faveolata and Porites astreoides), yet our results indicate that when the confounding effects of colony density and size were removed, selective corallivory existed only for the less dominant Porites porites. As changes in disturbance regimes result in the decline of dominant frame-work building corals such as Montastraea spp., the projected success of P. porites on Caribbean reefs through high reproductive output, resistance to disease and rapid growth rates may be attenuated through selective corallivory by parrotfish.
28 citations
TL;DR: The health of the coral assemblage and the similarity of responses across levels of protection suggested that negligible anthropogenic disturbance at the local scale was a key factor underlying the observed resilience.
Abstract: Coral reefs are damaged by natural disturbances and local and global anthropogenic stresses. As stresses intensify, so do debates about whether reefs will recover after significant damage. True headway in this debate requires documented temporal trajectories for coral assemblages subjected to various combinations of stresses; therefore, we report relevant changes in coral assemblages at Little Cayman Island. Between 1999 and 2012, spatiotemporal patterns in cover, densities of juveniles and size structure of assemblages were documented inside and outside marine protected areas using transects, quadrats and measurements of maximum diameters. Over five years, bleaching and disease caused live cover to decrease from 26% to 14%, with full recovery seven years later. Juvenile densities varied, reaching a maximum in 2010. Both patterns were consistent within and outside protected areas. In addition, dominant coral species persisted within and outside protected areas although their size frequency distributions varied temporally and spatially. The health of the coral assemblage and the similarity of responses across levels of protection suggested that negligible anthropogenic disturbance at the local scale was a key factor underlying the observed resilience.
21 citations
TL;DR: Parts of the most prevalent episode of coral bleaching ever recorded at Little Cayman, Cayman Islands, during the fall of 2009 are described and the method outlined here could be applied to other regions to find the optimal bleaching threshold and improve bleaching predictions.
Abstract: The global rise in sea temperature through anthropogenic climate change is affecting coral reef ecosystems through a phenomenon known as coral bleaching; that is, the whitening of corals due to the loss of the symbiotic zooxanthellae which impart corals with their characteristic vivid coloration. We describe aspects of the most prevalent episode of coral bleaching ever recorded at Little Cayman, Cayman Islands, during the fall of 2009. The most susceptible corals were found to be, in order, Siderastrea siderea , Montastraea annularis , and Montastraea faveolata , while Diplora strigosa and Agaricia spp. were less so, yet still showed considerable bleaching prevalence and severity. Those found to be least susceptible were Porites porites , Porites astreoides , and Montastraea cavernosa . These observations and other reported observations of coral bleaching, together with 29 years (1982–2010) of satellite-derived sea surface temperatures, were used to optimize bleaching predictions at this location. To do this a Degree Heating Weeks (DHW) and Peirce Skill Score (PSS) analysis was employed to calculate a local bleaching threshold above which bleaching was expected to occur. A threshold of 4.2 DHW had the highest skill, with a PSS of 0.70. The method outlined here could be applied to other regions to find the optimal bleaching threshold and improve bleaching predictions.
20 citations
TL;DR: In this article, the authors investigated the relationship between survivorship and reproductive mode (brooding vs. broadcast spawning) of sexual reproduction and found that survivorship was significantly higher in deeper habitats at three of the four fringing reefs and the semi-exposed inshore, highly sedimented reefs, showed higher juvenile survivorship than the mid-shelf and shelf edge reefs.
Abstract: 2 in 2005. Juvenile coral composition, relative abundances, survivorship and recruitment varied significantly across depth intervals within reefs and among reefs. Some species with high relative abundances in 2003 showed high survivorship in 2005 ( Siderastrea siderea (28.3% and 65% respectively), Porites astreoides (15.1% and 55.6%), and Diploria strigosa (7.5% and 45.2%)). Other taxa had relative low abundances but high survivorship ( Montastraea cavernosa (4.6% and 66.7%) and Stephanocoenia intersepta (4.6% and 48.3%)). Survivorship was significantly higher in deeper habitats at three of the four fringing reefs. Furthermore, the semi-exposed inshore, highly sedimented reefs, showed higher juvenile survivorship than the mid-shelf and shelf-edge reefs. There was no clear relationship between survivorship and reproductive mode (brooding vs. broadcast spawning) of sexual reproduction. Overall, only 78 new recruits were found in 2005.
20 citations
"A study on the recovery of Tobago's..." refers background or methods in this paper
...A low juvenile population dominated by brooding taxa with weedy life history strategies is common across Caribbean reefs (Miller et al., 2000; Moulding, 2005; Irizarry-soto and Weil, 2009; Manfrino et al., 2013)....
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...This distinction was made as small-sized corals tend to be sexually mature adults once larger than 2 cm (Chiappone and Sullivan, 1996;Miller et al., 2000; Irizarry-soto and Weil, 2009)....
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...Correspondence analysis (CA) was performed on eight genus groups found at each site, after removing all rare taxa, to explore the distribution of species composition across all sites (Irizarry-soto and Weil, 2009) using ordination analysis tools in the Vegan Package in R software....
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...To improve our understanding of post-bleaching recovery it is important to assess the impact of bleaching on coral assemblages and the ability of coral taxa to sexually reproduce within their given environment (Birrell et al., 2005; Smith et al., 2005; Irizarry-soto and Weil, 2009)....
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...Low numbers of Orbicella recruits have been well documented across Caribbean reefs (Hughes and Tanner, 2000; Irizarry-soto and Weil, 2009; Vermeij et al., 2011)....
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